1. Field of the Invention
This invention relates to an image forming apparatus such as an electrophotographic apparatus.
Herein, the image forming apparatus is an apparatus using, for example, the electrophotographic image forming method to form an image on a recording medium, and covers, for example, an electrophotographic copier, an electrophotographic printer (such as a laser printer or an LED printer), a facsimile apparatus and a wordprocessor.
2. Related Background Art
In an image forming apparatus using the electrophotographic image forming process, there has heretofore been adopted the process cartridge system in which an electrophotographic photosensitive body which is an image bearing member and process means acting on this electrophotographic photosensitive body are integrally made into a cartridge which is detachably attachable to the main body of the image forming apparatus. According to this process cartridge system, the maintenance of the apparatus can be done by a user himself without resorting to a serviceman and therefore, operability can be markedly improved. So, this process cartridge system is widely used in image forming apparatuses.
The above-described process cartridge system, however, is limited in developer capacity, i.e., toner capacity, and has the following weak points.
Particularly in the case of an image forming apparatus capable of effecting heavy duty printing, the process cartridge system having a small toner capacity increases the frequency of interchange of the process cartridge and usability becomes bad. Also, besides the toner, the constituent parts of the cartridge are also integrally interchanged, and this results in the rise of running cost.
So, the so-called toner replenishing system in which an apparatus such as developing means is provided on the main body side of an image forming apparatus and only a toner is supplied has become the mainstream in the image forming apparatuses capable of effecting heavy duty printing. The demerit of this toner replenishing system is that the maintenance such as the interchange of parts of consumption is almost impossible by the user and the maintenance by a serviceman is necessary.
Under the present situation as noted above, in recent years, there is being realized a toner replenishing system process cartridge system having the merits of the process cartridge system and the toner replenishing system.
This system is comprised of a process cartridge having a photosensitive drum which is an electrophotographic photosensitive body, and developing means for visualizing an electrostatic latent image formed on the photosensitive drum by a toner, a developer supplying unit, i.e., a toner supplying unit, for replenishing the developing means with a predetermined amount of toner.
This developing means has a toner density detecting device as developer density detecting means for detecting the density of the developer therein (the density of the toner), i.e., the mixing ratio of toner and carrier, and effects the toner replenishment from the toner supplying unit in conformity with the detected value by this toner density detecting device, thereby maintaining the density of the toner constant.
Also, the developing means has means for detecting the amount of toner in the toner supplying unit, and as this detecting means, use is made of one of various conventional sensors such as a piezo-sensor provided on the inner wall of a container, a sensor for detecting the amount of toner from the electrostatic capacity of the toner, and a light transmitting type sensor.
The toner supplying unit comprises a toner enclosing portion and a toner supplying portion, and is provided with a construction for sealing the toner by a seal member to prevent the leakage of the toner during distribution (transportation). The user moves or pulls out the seal member when he uses the toner supplying unit for the first time, thereby making the supply of the toner from the toner supplying portion.
By applying such a toner replenishing system process cartridge to an electrophotographic image forming apparatus, maintenance property, improved usability, low running cost, etc. are realized.
The toner supplying unit must be used after the seal member which has so far sealed the toner has been pulled out or moved during use. In the above-described example of the prior art, however, the amount of toner in the toner supplying unit can be detected, but it cannot be detected that the toner is in its suppliable state.
Therefore, if the image forming operation is performed when the seal member has not been pulled out or moved and the toner is not in its suppliable state, the replenishment of the developing means with the toner is not effected at all in spite of it being detected that a sufficient amount of toner is present in the toner supplying unit, thus resulting in a reduction in image density.
Also when due to some accident or other, the replenishment of the toner supply from the toner supply port of the toner supplying unit is not effected well, it is impossible to detect this, thus likewise resulting in a reduction in image density.
Accordingly, it is an object of the present invention to provide an image forming apparatus which reliably judges the forgetting of the pulling out of a seal member when a developer supplying unit is a new one, the bad opening and closing of the seal member, and further the state of the developer supplying unit as when the replenishment of the developer supply has not been sufficiently effected for some reason or other, can inform a user of these and is very useful to a user.
Other objects and features of the present invention will become more fully apparent from the following detailed description when read with reference to the accompanying drawings.